Elbow lock and alternator for actuating the same



May 5, 1953 D. M. THREEWIT 2,637,042

ELBOW LOCK AND ALTERNATOR FOR ACTUATING THE SAME Filed July 27. 1951 3 Sheets-Sheet l 4 I 2e 11 1 l Z3 is 45 a5" 7a .51; 52 as 45 1 4 4 4 44 41 40 50 41 44 mmvroza. Do/vnw M. limfimr May 5, 1953 M. THREEWIT ELBOW LOCK AND ALTERNATOR FOR ACTUATING THE SAME Filed July 2'7. 1951 3 Sheets-Sheet 2 ,WIIIIIIIIA I 'IIIIIIIIIZIZA v H INVENTOR. 00mm M Tyne-m7 y 1953 D. M. THREEWIT 2,637,042

ELBOW LOCK AND ALTERNATOR FOR ACTUATING THE SAME Filed July 27, 1951 3 Sheets-Sheet 5 Patented May 5, 1953 ELBOW LOCK AND ALTERNATOR FOR ACTUATING THE SAME Donald M. Threewit, Inglewood, Calif., assignor to Northrop Aircraft, Ina, Hawthorne, Calif a corporation of California Application July 27, 1951, Serial No. 238,825

4 Claims. (01. s--12.2)

The present invention relates to artificial arms, and more particularly to above-elbow arms of the type wherein the forearm portion is connected to an upper arm portion by an elbow joint and locking mechanism.

Among the obiecti-cns common to practically all prior elbow locks is that they are heavy, excessively complicated and expensive to manufacture, require frequent adjustment, and are susceptible to damage under the shocks and stresses of normal use. As a result, none of the prior elbow locks have been completely satisfactory, and there has long been room for considerable improvement in elbow lock design. A primary object of the present invention, therefore, is to provide a new and improved elbow lock that is light in weight, durable, simple and inexpensive to manufacture, and free from service troubles.

Another object is to provide an elbow lock that is positive in action, and that enables the forearm to be locked in a plurality of closely spaced angular positions.

A further object of the invention is to provide a new and improved device for alternately looking and unlocking the elbow lock responsive to successive pulls on a pull cord.

Still another object of the invention is to provide an elbou lock embodying a minimum number of parts, and in which the parts are of relatively simple form.

In the present invention, the elbow lock is comprised of a toothed sector, fixed to the forearm coaxial with the elbow hinge pivot, the said sector being engaged by a pivoted locking lever that is mounted for swinging movement in a plane passing through the axis of the elbow hinge pivot. The free end of the locking lever is engageable in the teeth of the sector to prevent movement of the forearm relative to the upper arm, and the lever is cammed into engagement with the sector teeth by a rotatable cam having alternate high and low portions on the periphery thereof. The cam is rotated between the lockin position wherein the lever is released and engaged in the sector teeth, and anunlocking position wherein the lever is lifted out oi engagement with the sector teeth by the high portions of the cam. Rotation of the cam is effected by ratchet means including a ratchet wheel fixed to the cam, and a lever arm mounted for swinging movement about the center of the ratchet wheel. A spring-pressed pawl on the lever arm engages the ratchet Wheel to advance the cam from one of its positions to the other each time the lever arm is rocked. A control cord is attached to the lever arm and to the usual shoulder harness, so that the elbow can be locked and unlocked by successive shoulder shrugs.

The foregoing and other objects and advantages of the present invention will become apparent to those skilled in the art upon con sideration of the following detailed description of the presently preferred embodiment thereof, reference being had to the accompanying draw ings, wherein:

Figure 1 is a side elevation of an above-elbow arm embodying the principles of the invention;

Figure 2 is an enlarged transverse vertical section through the elbow hinge axis, taken alon the line 2-2 in Figure 1;

Figure 3 is a sectional view through the elbow mechanism, taken along the line 3-3 in Figure 2;

Figure 4 is another sectional view through the elbow mechanism, taken along the section line A l in Figure 2;

Figure 5 is a section taken at 5-5 in Figure 2;

Figure 6 is a section taken at 6-43 in Figure 5, showing the ratchet mechanism for advancing the cam; and

Figure 7 is a sectional view taken at il in Figure 5.

In the drawings, the arm of the invention is designated in its entirety by the reference numeral i8, and is seen to comprise an upper arm portion H, lower arm portion 12, and elbow mechanism [3 connecting them together for relative swinging movement. Mounted on the distal end of the lower arm portion [2 is a normally closed hook M, which is opened by a Bowden cable control wire it. The control wire [5 passes up along the arm through a springwound conduit 15, and is attached at its upper end to the usual shoulder harness so that a forward movement of the shoulder produces a pull on the control wire It to open the hook.

Both the upper arm portion H and lower arm portion I: are preferably, although not necessarily, formed of plastic shell construction, which is built up by laminating fabric such as cotton stookinet over suitable plaster forms, irnpregnating the fabric with liquid resin, and ow ing the resin in an oven. The upper arm portion H is the stump socket, and is therefore shaped to provide a good fit over the stump. Buckles Zll are attached by straps Hi to the front, rear, and outer sides of the upper arm portion l i, and straps of the shoulder harness (not shown) pass 3 through the buckles to hold the arm if; on the stump.

The mechanism of the elbow i3 is attached to the upper arm portion I l by means of aturntable member 22 having a serrated, annular flange 23 that is embedded in the bottom end of the upper arm portion II; the said turntable member being assembled with the upper arm shell at the time the stockinet material is formed over the mold and cured in the oven. The turntable member 22 is provided on its inside surface with an upwardly facing, annular shoulder 24, and seated on the shoulder is a circular plate 25 of reinforced phenolic resin. Four fillister head screws 26 pass downwardly through holes in plate 25 and in a second plate 3], and are screwed into the base of a yoke 3!. The plate 30 is attached by four screws (not shown) to the top surface of the yoke 3|, and sup-ports the locking lever, cam, and alternator mechanism, all of which will be described in detail presently.

The yoke 3| is referably made of high strength aluminum alloy for lightness, and is formed with two fore and aft spaced, arcuate base portions 32, 32 (see Figure 5) which are connected together on opposite sides by downwardly projecting, flatsided ears 33. The top surfaces of the base portions 32, 32 bear against the bottom surface 34 of the turntable member 22, and the turntable is therefore clamped between the yoke 3| and the plate 25. The elbow mechanism is thus frictionally clamped to the turntable and can be angularly adjusted thereon by loosening the screws 2 and turning the elbow. The screws are then tightened again to secure the elbow in adjusted position.

The two ears 33 of the yoke are provided with transversely alined holes 35, and pressed into these holes are bronze bushings 36. Rotatably disposed within the bushings is an externally serrated tubular shaft 40, which is provided with internally serrated journal sleeves 4| to turn within the bushings. The ends of the shaft project laterally outward beyond the bushings, and fixedly mounted thereon is a saddle 42. saddle 42 has a semi-cylindrical body portion provided with a skirt (not shown) that projects down into the interior of the forearm shell, where it is bonded to the plastic material when the shell is formed on the plaster cast and cured in the oven. Side arm portions 43 project upwardly from the saddle on opposite sides thereof, and these are provided with serrated holes 44 (see Figure 2) which receive the ends of the serrated shafts 40. The ends of the tubular shaft are closed by end caps 45, which are drawn against the end of the shaft by screws 46; the said screws being threaded into the ends of a rod 50 extending through the center of shaft 40.

Mounted on the right hand end (as viewed in Figure 2) of the shaft 40 is a toothed section 5| having an internally serrated bore 52 to receive the serrations of the shaft. The sector is positioned axially on the shaft by means of a spacer sleeve 53, one end of which bears against the sector, and the other end thereof abutting against the journal sleeve 4| at the opposite side of the elbow. By virtue of the inter-meshing serrations on the shaft 40, saddle ears 43, and sector 50, the three parts are interlocked or splined together in a manner to prevent relative rotation, and the shaft and sector are therefore rigidly connected to the forearm I2 to rotate therewith as an integral unit. Shoulders 54 and 55 (Figures 3 and 4) on opposite ends of the sector 5| are The engageable with a rubber bumper 56 to limit the swinging movement of the forearm in both directions, the said bumper being mounted on a shaft 5'! which is secured at its ends, in holes 60 in the yoke ears 33.

The teeth GI of the sector 51 are engageable by the free end of a pivoted locking lever 62, the other end of said lever being disposed between two laterally spaced lugs 63 which project downwardly from the underneath surface of the plate 30. A pin 64 is passed through alined holes in the lugs 63 and lever 62 to provide a pivot. A wire torsion spring 65 has laterally spaced coil portions which are wrapped around the projecting ends of pin 64 as shown in Figure 5, and a central loop portion that passes over the top of lever 62 to exert a downward thrust on the latter tending to press the lever into engagement with the teeth of sector 5|.

The free end of the flever 62 is disposed between and slidably engages two laterally spaced guide lugs 66 projecting downwardly from the underside of plate 3i). These guide lugs function to brace the lever against lateral deflection under stress exerted by the sector 5|, and their function is to relieve the lever of bending stresses. The lever 62 is also swingable vertically between two other laterally spaced, downwardly projecting lugs 19 and H, the latter providing journal support for a, rotatable cam assembly, which is designated in its entirety by the reference numeral 13.

The cam assembly 13 consists of a shaft '14 having a three-sided, triangularly shaped cam 15 formed integrally therewith at one of its ends. Spaced axially along the shaft 14 from cam 15 is an integral ratchet wheel 16, and the portion of the shaft projecting from the far side of the ratchet wheel is journaled for rotation in an ear Tl projecting downwardly from the plate 30. A journal portion is provided on the shaft immediately adjacent the cam 15, and this is rotatably received within a bearing bore in the lug H.

As best shown in Figure 2, the cam 15 is provided on its periphery with a plurality of equally spaced, alternate high and low portions. In the presently preferred embodiment of the invention, the cam is in the form of an equilateral triangle, as shown, of which the apexes form the high portions and the flat sides form the low portions. The invention is not limited in any way to a triangular cam, however, as other cam forms may be used. The high portions of the cam are engageable with the underside of the lever 62 as the cam is rotated, thereby lifting the lever out of engagement with the sector teeth against the pressure of the spring '6 5. A notch BI is provided in the bottom surface of the lever 62 to engage the points of the cam when the lever is fully raised, so as to prevent the cam from inadvertently slipping to one side or the other. When the shaft is turned 60 degrees from the lever-raise position, a flat side of the cam is presented to the lever, and the latter is depressed into engagement with the sector teeth by the springs 65. Thus, with each 60 degree increment of rotation, the cam 15 alternately raises and lowers the locking lever 62, causing the elbow to be unlocked or locked, as the case may be.

The cam shaft 14 is progressively advanced in 60 degree increments by an operating lever arm 82 having a spring-pressed ratchet pawl 83 that engages the ratchet wheel 16. The lever arm is bifurcated, and the ratchet wheel and detent are disposed between the two legs thereof. The

lever arm is swingably'supported on the camshaft-M and is urged in the counterclockwise direction, as viewed in Figures 6 and 7, by a wire torsion spring 84; such counterclockwise movement being limited by a stop spring 85 which is fastened to the bottom surface of the plate and engages the ends of the ratchet wheel teeth. There are six teeth on the ratchet wheel 16, which are spaced apart degrees from one another, and consequently, each time that the lever arm 82 is rocked in a, clockwise direction, the cam shaft 14 is advanced by 60 degrees.

The operating lever is rockedby means of a control cord 86 which is attached at one end to a terminal fitting 8? on the lever, The fitting 8 1 has a pin 95 (see Figure 6) which is inserted into a hole in the endof the lever arm 82. The pin is free to turn, and the fitting 81 is therefore free to follow the position of the cord 8'5 without bending the latter. The cord 86 passes upwardly through a hole 9! in plate 32 and through an arcuate slot 92 in plate 3i! and emerges through an opening (not shown) in the upper arm portion Ii to extend upwardly along the outside of the latter. Near the upper end of the arm, the control cord 86 is guided through a strap loop 93, and the end of the cord is provided with a terminal fitting 94 by which it is connected to the shoulder harness.

The operating movement for locking and unlocking the elbow is provided by shoulder shrugs, which cause a pull to be exerted on the control cord 86. Each time that the control cord 86 is pulled, the lever arm 82 is rocked, causing the cam it to be advanced 60 degrees from its preceding position. This causes the locking lever 62 to be alternately lifted out of engagement with the teeth of sector 5i, and then lowered into engagement therewith. Thus, successive shoulder shrugs causes the elbow lock to be alternately locked and unlocked.

The forearm I2 is raised and lowered by means of a forearm fiexion control cable 95 which is attached at its lower end to a metal strap 96 fixed to and projecting outwardly from the forearm. The cable 95 passes upwardly along the arm to a flexible conduit 97 which is anchored at 8, and the upper end of the cable is provided with a terminal fitting $39 which is attached to one of the straps of the shoulder harness.

The mechanism of the elbow lock is enclosed within an outer shell 108, which may be formed of metal or molded from plastic impregnated stockinet of the same type as that used in the arm shell. The outer end of the cover I00 is spherically curved to maintain minimum clearance with the saddle &2 for all positions of the forearm i2, and the sides of the housing are flattened as shown in Figure 2, to receive the arms 43 of the saddle.

While I have shown and described in considerable detail what I believe to be the preferred form of my invention, it is to be understood that such details are merely illustrative of the principles of my invention, and that various changes may be made in the shape and arrangement of the several parts without departing from the broad scope of the invention, as defined by the appended claims.

I claim:

1. In an artificial arm having an upper arm portion, a forearm portion, and an elbow connecting them together for relative swinging movement, an elbow lock comprising, in combination, a toothed sector fixedly connected to 6J1: saidfcrearm portion coaxial with the pivot axis of said elbow joint, a locking lever pivoted, on. said upper armportion for swinging in a planev perpendicular to the plane of saidv sector, said lever being engageable in the teeth ofv said sector to lock said arm portions against relative movement, spring means urging said lever into engagement with said sector teeth, a rotatable cam jou-rnaled on said upper arm portion and engageable with said lever. saidcam being 0perable in one position to lift said lever outv of, engagement with said sector teeth, and in an-' other position to release said lever so that said spring means is enabled to depress the same into engagement with said sector teeth, a ratchet wheel fixed. to saidcam, a pivoted operating lever meu-ntedcoaxial with said ratchetwheel, and a ratchet pawl on said operating lever engageable with the teeth of said ratchet wheel to advance said cam from one of said positions to the other each time the operating lever is actuated.

2. In an artificial arm having an upper arm portion, a forearm portion, and an elbow connecting them to ether for relative swinging movement, an elbow lock comprising, in combination, a toothed sector fixedly connected to said forearm portion coaxial with the pivot axis of said elbow joint, a locking lever pivoted on said upper arm portion and engageable in the teeth of said sector to lock said arm portions against relative movement, means slidably engaging the free end of said lever for bracing the same against lateral deflection under stress exerted by said sector, a cam of triangular crosssection rotatably supported on said upper arm portion, the points of said cam being engageable with said lever to lift the same out of engagement with said sector teeth, and means for advancing said cam in 60 degree increments, whereby said lever is alternately lifted out of engagement with said sector teeth and lowered into engagement therewith responsive to successive control movements.

3. In an artificial arm having an upper arm portion and a lower arm portion, an elbow fixed to the end of said upper arm, a transverse shaft fixed to said forearm and journaled in said elbow housing, a toothed sector fixed to said shaft and rotatable therewith, a locking lever pivoted on said housing for swinging movement in a plane passing through the axis of said shaft, said lever being engageable in the teeth of said sector to lock said arm portions against relative movement, means slidably engaging the free end of said lever for bracing the same against lateral deflection under stress exerted by said sector, spring means urging said lever into engagement with said sector teeth, a cam rotatably mounted on said housing and having a plurality of equally spaced, alternately high and low portions provided on the periphery thereof, said high portions being engageable with said lever to lift the same out of engagement with said sector teeth against the pressure of said spring means, a ratchet wheel fixed to said cam coaxial therewith, an arm pivoted for rocking movement about the center of said ratchet wheel, a spring-pressed pawl on said arm engageable with the teeth of said ratchet wheel, and a control cord attached to said arm, successive pulls on said control cord causing said arm and pawl to advance said ratchet wheel and cam alternately to locked and unlocked positions.

4. In an artificial arm having an upper arm portion, a forearm portion, and an elbow connecting them together for relative swinging movement, an elbow lock comprising, in combination, a toothed sector fixedly connected to one of said arm portions coaxial with the pivot axis of said elbow, a locking lever pivoted on the other of said arm portions and engageable in the teeth of said sector to lock said arm portions against relative movement, spring means urging said lever into engagement with said sector teeth, a rotatable cam journalled on said other arm portion and engageable with said lever, said cam being operable in one position to lift said lever out of engagement with said sector teeth, and in another position to release said lever so that spring means is enabled to depress the same into engagement with said sector teeth, a pivoted operating lever mounted coaxial with said cam, and a one-way driving connection between said lever and said cam operable to advance the latter from one of said positions to the other each 5 time the operating lever is oscillated.

DONALD M. THREEWIT.

References Cited in the file of this patent UNITED STATES PATENTS 10 Number Name Date 2,477,463 Otterman July 26, 1949 FOREIGN PATENTS Number Country Date 303,664 Germany Feb. 11. 1918 327,491 Germany Oct. 13, 1920 

